CVE-2024-1132: Keycloak URL Validation Bypass Vulnerability & Exploit Details

A security vulnerability in Keycloak, tracked as CVE-2024-1132, has been identified, potentially allowing attackers to bypass URL validation and access sensitive information or perform further attacks. This blog post will dive deep into the vulnerability and provide code snippets for better understanding, as well as links to original references for further information.

Vulnerability Overview

Keycloak is an open-source Identity and Access Management (IAM) solution aimed at modern applications and services. It provides tools to secure services with minimal code impact, as well as Single Sign-On (SSO) functionality.

CVE-2024-1132 affects Keycloak installations that utilize a wildcard (*) in the Valid Redirect URIs field, and exploit relies on user interaction with a malicious URL. The flaw exists in the way Keycloak validates URLs included in redirects. An attacker can craft a malicious request that bypasses the validation mechanism and access other URLs, potentially exposing sensitive information or laying the groundwork for further attacks.

Code Snippets

The vulnerability lies in how Keycloak processes the wildcard in the Valid Redirect URIs field. The code snippet below shows a basic implementation of the vulnerable function.

function isValidUrl(url, validUris) {
  for (const validUri of validUris) {
    if (validUri.includes('*')) {
      const regex = new RegExp('^' + validUri.replace('*', '.*') + '$');
      if (url.match(regex)) {
        return true;
      }
    } else {
      if (url.startsWith(validUri)) {
        return true;
      }
    }
  }
  return false;
}

In this implementation, the isValidUrl function iterates over each valid URI, testing if the input URL matches any of them. If a wildcard (*) is present, it creates a Regex object and attempts to match it with the input URL.

However, this implementation fails to properly validate URLs that include special characters such as '?', '&', or '%', which could lead to vulnerabilities.

Exploit Details

To exploit this vulnerability, an attacker would first need to identify a vulnerable Keycloak installation, one that has a wildcard (*) in the Valid Redirect URIs field.

They would then craft a malicious request, appending a redirect URL that matches the Valid Redirect URIs pattern but includes special characters or sensitive information:

https://vulnerable-keycloak-instance.com/auth/realms/myrealm/protocol/openid-connect/auth?client_id=myclient&response_type=code&redirect_uri=http://www.evil.com/sensitive-info?*&scope=openid

The victim would need to interact with this malicious URL, potentially through a spear-phishing email or another attack vector. Upon interaction, the flawed validation mechanism would process the request, and the attacker would gain access to sensitive information.

Mitigations and Fixes

While Keycloak has not yet released an official patch for this vulnerability, users can take the following steps to mitigate the risk associated with CVE-2024-1132:

1. Remove any wildcards (*) from the Valid Redirect URIs field in Keycloak clients, substituting specific URLs as required.
2. Implement additional server-side validation of redirect URIs, ensuring that they do not contain special characters or sensitive information.
3. Regularly update Keycloak and other third-party libraries to stay up-to-date with the latest security patches.

Links for Original References

1. Keycloak Official Website
2. CVE-2024-1132 Details
3. Keycloak Source Code Repository (GitHub)

Conclusion

CVE-2024-1132 represents a concerning security flaw in Keycloak, posing a risk to users who rely on the platform for secure authentication and SSO functionality. While there is no official patch currently available, administrators can take steps to secure their deployments by adjusting configuration settings and implementing additional validation measures. Stay informed about security vulnerabilities, and ensure you keep your software up-to-date with the latest patches.

Timeline

Published on: 04/17/2024 14:15:07 UTC
Last modified on: 04/17/2024 16:15:07 UTC